- Haskell-Cafe - Haskell.org

Haddock and the type inference
by Yves Parès 10 Jul '11

10 Jul '11

Hello Café, As far as I know, there is currently no way to tell haddock to run the type inferer to document functions without explicit type signature. Is that done on purpose (e.g. to force the developpers to write at least the type signatures of the public API, which is a fair reason) or is it a limitation? Is it planned to add that support to haddock?

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Re: [Haskell-cafe] NLP libraries and tools?
by wren ng thornton 10 Jul '11

10 Jul '11

(Psst, the nlp list is <nlp(a)projects.haskell.org> :) On 7/9/11 3:10 AM, Jack Henahan wrote: > On Jul 7, 2011, at 10:53 PM, wren ng thornton wrote: >> I can't help but be a (meta)theorist. But then, I'm of the firm opinion >> that theory must be grounded in actual practice, else it belongs more to >> the realm of theology than science. > > Oof, you're liable to wound my (pure) mathematician's pride with remarks like that, wren. :P How's that now? Pure mathematics is perfectly grounded in the practice of mathematics :) I've no qualms with pure maths. Afterall, mathematics isn't trying to model anything (except itself). The problems I have are when the theory branch of a field loses touch with what the field is trying to do in the first place, and consequently ends up arguing over details which can be neither proven nor disproven. It is this which makes them non-scientific and not particularly helpful for practicing scientists. Linguistics is one of the fields where this has happened, but it's by no means the only one (AI, declarative databases, postmodernism,...) There's nothing wrong with not being science. I'm a big fan of the humanities, mathematics, and philosophy. It's only a problem when non-science is pretending to be science: it derails the scientists and it does a disservice to the non-science itself. Non-science is fine; pseudo-science is the problem. For the same reason, I despise math envy and all the pseudo-math that gets bandied about in social sciences wishing they were economics (or economics wishing it were statistics, or statistics wishing it were mathematics). -- Live well, ~wren

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[ANN] PAM library, Iptables web-interface
by Evgeny Tarasov 10 Jul '11

10 Jul '11

Hello! I'd like to announce my project called Iptadmin. It's a web interface for linux Iptables firewall [1]. It supports just few Iptables options by now. The main feature of Iptadmin is user friendly help messages. Iptadmin works in a daemon mode. It doesn't keep any auxiliary information in a system, firewall configuration is taken from the «iptables-save» script. All changes is made by Iptables calling. Firewall rules are saved by «/etc/init.d/iptables save» script. Several linux distributions such as Debian require additional Iptables configuration. Iptadmin uses PAM [2] authentication. Access is granted for root and for any other user with membership in «iptadmin» system group. Iptadmin is written using Happstack, so it doesn't support https yet. To prevent sending system password by network in plain text, the web interface is listening only on loopback network interface. In order to access Iptadmin remotely user should setup https proxying using external web server. There is also dedicated library for parsing and printing Iptables rules [3]. While working on Iptadmin I've implemented library with subset of PAM api bindings[4]. A code of my project is licensed under BSD3. Sources are uploaded to hackage [3,4,5]. More information can be found on a project homepage[6]. [1] http://www.netfilter.org/ [2] http://www.kernel.org/pub/linux/libs/pam/ [3] http://hackage.haskell.org/package/iptables-helpers-0.3 [4] http://hackage.haskell.org/package/pam-0.1 [5] http://hackage.haskell.org/package/iptadmin-1.0.0 [6] http://iptadmin.confmgr.org -- Best regards, Evgeny Tarasov

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Cabal uninstall
by Andrew Pennebaker 09 Jul '11

09 Jul '11

Please add an automated uninstall option for Cabal packages. It's a pain to remove them manually, and the user expectation based on other package managers (Gem, Aptitude, MacPorts, Homebrew, Yum, Emerge) is that "cabal uninstall"/"cabal remove" does the intuitive thing: remove packages and their dependencies. Cheers, Andrew Pennebaker www.yellosoft.us

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Re: [Haskell-cafe] Call for GUI examples - Functional Reactive Programming
by John Lato 09 Jul '11

09 Jul '11

From: Chris Smith <cdsmith(a)gmail.com> > > On Fri, 2011-07-08 at 08:08 +0200, Heinrich Apfelmus wrote: > > Do you know any *small GUI programs* that you would *like* to see > > *implemented with Functional Reactive Programming?* > > This isn't really a specific application, but what I'd like to see most > from FRP is an example of something that involves moving between windows > and dialog boxes. All of the GUI-based FRP examples I've seen so far > involve interactions in a specific GUI layout. It's unclear to me how > FRP extends into a situation like: > > - There's a starting window showing several options for what to do > - When the user chooses an option, that window closes, and a new one > opens with that activity. > - In response to some actions, dialog boxes appear with their own > interactions. > > It's not clear to me if anyone in FRP has an idea of how stuff like this > fits in. Is there some FRP trick to handle this declaratively? Or > would you just say each move to a new window ends or pauses one network > of events and behaviors, and starts a new one? I can show you how I've been handling this with reactive-banana and gtk2hs. As a small example, the "File->Open" command is meant to open a new project. The codez: > maybeEvent0 :: Typeable a => Action -> IO (Maybe a) -> NetworkDescription (Event a) > maybeEvent0 act ops = do > (addHandler, runHandlers) <- liftIO newAddHandler > liftIO $ on act actionActivated $ ops >>= maybe (return ()) runHandlers > fromAddHandler addHandler > -- | Load a saved project file > openHandler :: ActionGroup -> Window -> NetworkDescription (Event (String, HTree)) > openHandler actGrp _win = do > act <- liftIO openAction > liftIO $ actionGroupAddActionWithAccel actGrp act Nothing > maybeEvent0 act openProjectDialog > openProjectDialog :: IO (Maybe (String, HTree)) > openProjectDialog = do > fc <- fileChooserDialogNew (Just "Select a project file") > Nothing > FileChooserActionOpen > [] > fileChooserSetSelectMultiple fc False > dialogAddButton fc stockCancel ResponseCancel > dialogAddButton fc stockOk ResponseOk > widgetShowAll fc > resp <- dialogRun fc > case resp of > ResponseOk -> runMaybeT $ do > fp <- MaybeT $ fileChooserGetFilename fc > liftIO $ widgetDestroy fc > (fp, ) <$> liftIO (readProject fp) > _ -> widgetDestroy fc >> return Nothing The `openHandler` function connects the Gtk signal to the reactive-banana framework. This uses the helper `maybeEvent0`, which filters an IO action and triggers a reactive-banana Event when that IO action actually returns a value. I've been using this pattern for most of my modal dialogs, and I think it works very well. The one dialog I haven't used it for is the starting window, which is straight-line imperative code. I don't yet have any non-modal dialogs or alternate windows, but there shouldn't be a problem. There's nothing special about which window a widget is in; it can be connected to the FRP framework just like a widget in the main window. John L.

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Re: [Haskell-cafe] NLP libraries and tools?
by wren ng thornton 09 Jul '11

09 Jul '11

On 7/7/11 3:50 AM, Aleksandar Dimitrov wrote: > It's actually a shame we're discussing this on -cafe and not on -nlp. Then > again, maybe it's going to prompt somebody to join -nlp, and I'm gonna CC it > there, because some folks over there might be interested, but not read -cafe. Quite :) > When you mentioned Arabic for producing sentences that go on for ages > you don't really need to go that far. I have had the doubtful pleasure of > reading Kant and Hegel in their original versions. In German, it is sometimes > still considered good style to write huge sentences. I once made it a point, > just to stick it to a Kant-loving-person, to produce a sentence that spanned 2 > whole pages (A4.) It wasn't even difficult. The Romans were big fans of that too (though there's only a small group of folks interested in doing NLP on Latin these days). I've only read Hegel et al. in translation, but the Latin I've read falls nicely into the notion of "span". It doesn't, however, always fall nicely into a clause-based approach like Japanese does. Then again, that could be due to the poetic/rhetorical nature of the texts in question. I wonder if there's been any computational attempt to make the notion of span or discourse atoms rigorous enough for pragmatic use... > I'm very much a "works for me" person in these matters. Mostly because I'm tired > of linguists fighting each other over trivial matters. Give me something I can > work with already! I can't help but be a (meta)theorist. But then, I'm of the firm opinion that theory must be grounded in actual practice, else it belongs more to the realm of theology than science. -- Live well, ~wren

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video for linux two (v4l2) bindings
by Claude Heiland-Allen 09 Jul '11

09 Jul '11

Greetings all, I uploaded 4 new packages that may be of interest: bindings-linux-videodev2 0.1 - bindings to Video For Linux Two (v4l2) kernel interfaces http://hackage.haskell.org/package/bindings-linux-videodev2-0.1 bindings-mmap 0.1 - bindings to mmap for POSIX http://hackage.haskell.org/package/bindings-mmap-0.1 bindings-libv4l2 0.1 - bindings to libv4l2 for Linux http://hackage.haskell.org/package/bindings-libv4l2-0.1 v4l2-examples 0.1 - video for linux two examples http://hackage.haskell.org/package/v4l2-examples-0.1 The first wraps the low-level structures and ioctls of the V4L2 API. The second wraps the raw mmap/munmap functions and constants (which I couldn't seem to find on hackage, only higher level wrappers which I couldn't use for various reasons). It would make more sense for this to be folded into bindings-posix at some point. The third wraps libv4l2, which provides an interface very similar to the use of V4L2 ioctls, but the library adds extra capabilities behind the scenes (I'm led to believe colour space conversion is one of them) which is hopefully useful. And the last is a crude example dumping frames from a video device (like a webcam) to stdout in YUV4MPEG2 format. The code is *very* low-level and imperative (almost a direct translation from the C example provided on the linuxtv API reference), there is plenty of room for a much nicer layer to (for example) get video data into RePa arrays or OpenGL textures. As these are raw bindings, documentation is best found upstream. Thanks to Maurício C. Antunes's package for making this possible, I recommend it: http://hackage.haskell.org/package/bindings-DSL Claude -- http://claudiusmaximus.goto10.org

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Re: [Haskell-cafe] Call for GUI examples - Functional Reactive Programming
by Daniel Patterson 08 Jul '11

08 Jul '11

Forgot to cc the list On Jul 8, 2011, at 11:20 AM, Daniel Patterson wrote: > On Jul 8, 2011, at 3:51 AM, Heinrich Apfelmus wrote: >> Jason Dagit wrote: >>> Heinrich Apfelmus wrote: >>>> Do you know any *small GUI programs* that you would *like* to see >>>> *implemented with Functional Reactive Programming?* >>>> >>>> I would love to hear your examples, so that I can try to convert them to FRP >>>> style and test my library against them! >>> How about a GUI for darcs? >> >> This would involve a lot of functionality unrelated to GUIs. Could you break it down to a minimal "GUI-only" example that still gets the point across? > > > What about something that just showed the list of patches for a given repository, which would update when the repository changed? That is deadly simple, but could still be somewhat useful (ie, have it track a relatively central repo, and running on a screen somewhere in the metaphorical office). It would also be wonderful to start on a GUI for darcs, and I could say it might interest _me_ in taking a stab at improving it :) And it might be an example of the kind of open system that was mentioned earlier > > Daniel

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Using Acid-State for IPC?
by Dmitri O.Kondratiev 08 Jul '11

08 Jul '11

Hi, I am wondering if Acid-State (http://hackage.haskell.org/package/acid-state) can be used to share data between processes running in different address spaces? For example, one demon system process (not thread!) periodically collects data from Web and stores it in a list. On regular intervals this process checkpoints the list to a disk file. Another independent process randomly starts and reads this list from the checkpoint file. Can this simple scenario be done with Acid-State? Any conflicts accessing checkpoint file from two system processes simultaneously? What other Haskell libs can be used for such a task? Thanks!

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CfP: Haskell Workshop in Leipzig, Germany, October 7
by Johannes Waldmann 08 Jul '11

08 Jul '11

Call for submissions for our local Haskell Workshop in Leipzig, Germany. Tutorials, talks, demonstrations ... everything welcome. Workshop language is German (mainly), and English (by request). Submission deadline: August 20, Workshop date: October 7 http://portal.imn.htwk-leipzig.de/events/hal6-haskell-workshop Best regards, Johannes Waldmann.

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